Placogorgia coronata first documented record in Italian waters: Use of trawl bycatch to unveil vulnerable deep-sea ecosystems

Despite the pluri-decennial history of bottom trawling monitoring in the Italian Sea, limited attention has been given to the study of cold water corals (CWC) present in the bycatch.

This study assessed bottom trawl discards of a red shrimp fishery in the Ligurian Sea, where the rare Mediterranean CWC species Placogorgia coronata was repeatedly found, being the first taxonomic record of this species in Italian waters. Additionally, remotely operated vehicle (ROV) surveys where undertaken to describe the substrate in the trawled area.

The ROV surveys highlighted the presence of a dead white coral framework, supporting the hypothesis that P. coronata, probably thriving on coral rubble, occurs here due to the natural protection to trawling offered by the coral matrix. It is however stated that trawlers may accidentally affect these secondary hard grounds, as demonstrated by the discard content. The results of the long-term monitoring of the catches highlighted a removal rate of up to one colony every two trawling operations.

The authors conclude that the occurrence of CWC species with low resilience to fishing disturbance is among the required information for the identification of fishing restriction zones designed to protect deep vulnerable marine ecosystems.